This invention relates generally to the processing of photosensitive sheet material and, more particularly, is concerned with the processing of two-sided photosensitive sheet material with a minimal amount of liquid processing solution, such as developer solution.
Photosensitive sheet material (PSM), as used herein and with which this invention is concerned, is intended to include a substantially flexible base sheet or web having a coating of photographic emulsion carried on at least one of the major faces of the sheet. As a descriptive term used herewith, "sheet " shall mean suitable materials of either discrete or indefinite length. Suitable materials may include film, web or plate. Commonly, the PSM emulsion includes a plurality of layers wherein each layer is designed to produce a specific result when allowed to react with developer solution. For example, in the photographic art, reproduction of a normal image is commonly accomplished by exposing a photosensitive material such as, for example, a photographic film, to visible light reflected from an object or image, and then the exposed PSM (film) is thereafter developed to produce a negative reproduction on a flexible, transparent substrate. Development of such flexible PSM commonly includes a series of processing steps such as immersing the emulsion-carrying substrate in a developer solution to bring forth the desired image followed by immersion in a fixer solution and thereafter subjected to one or more water washing steps. As used herein, reference to a "processing solution " shall include water and water washing.
More particularly, photosensitive materials, as envisioned by this description, are those that are selectively responsive to radiant energy, whether transmitted, reflected or emitted. PSM responsive radiant energy includes the expanded spectrum of visible, ultraviolet, infrared and X-ray.
The art of X-ray photography is similar to reflected radiation photography except that the radiation energy passes through the examination object to be relatively screened dependent on density and other characteristics of the object. Such relative screening produces energy variation patterns in a radiation wave through and across an irradiated area. Certain photosensitive materials respond to such radiation energy with such sensitivity as to produce a shadow image of the examination object showing only elements of selected common characteristics, e.g. bone, for example. Due to the potential for radiation energy such as X and gamma ray to injure the irradiated object, radiation photography in such cases is conducted at minimum levels of intensity or energy density. To compensate for a reduced incidence of excitation energy, many types of X-ray films are prepared with emulsion coated on both surfaces of a transparent substrate. Development of such two-sided PSM requires great attention to all process control parameters such as time, temperature and developer/film solution agitation imposed simultaneously upon both surfaces of the PSM coated film.
Developer solutions comprise combinations of chemicals, generally in aqueous solution, wherein each of the chemicals is chosen to react with one or more of the constituents in one or more of the layers of the emulsion to produce a specific result. The quality of the resulting product depends, to a large extent, upon the nature of the physical contact of the PSM with the developer solution. However, chemical reactions which occur during development of a PSM generate by-products that are released in the developer solution which, in turn, renders the developer solution less effective. Therefore, it is important that during a development process, developer solution in contact with the PSM be cyclically exchanged to continuously expose the PSM to fresh or relatively less-depleted solution.
The type of apparatus with which this invention is concerned includes one or more film processing cells, each including a plurality of internal cavities for containing a processing solution, such as a developer solution, so that the liquid body of solution contained within the cell cavities substantially is a flowing film. During a processing step with such a substantially thin reservoir cell, a PSM film end is inserted through an opening provided in each cell and into the body of solution contained therein and conveyed through the cell so that the processing solution acts upon the PSM in a desired manner and for a predetermined period of time. The apparatus may include a series of such reservoir cells arranged in a side-by-side arrangement so that conveyance of a PSM in sequence through the cells exposes the PSM in succession to the working fluid contained within each cell. The number of cells, cavities within each cell and the characteristics of the solution contained within each cell depends upon the characteristics which the PSM is desired to exhibit when processed. In addition, the rate at which the PSM is conveyed through any one cell and the rate of replenishment of the fluid contained within the one cell are commonly coordinated to control the exposure of the PSM to the working fluid within the one cell.
A reservoir cell of the aforedescribed class is shown and described in U.S. Pat. No. 5,266,994, the disclosure of which is incorporated herein by reference. In one embodiment of the reservoir cell described in the referenced patent, there is provided a plurality of elongated woven fabric loops which are secured to the upper part of the reservoir cell so that the bight of the loop extends downwardly into the reservoir cavity. A PSM which is moved through the cavity of such a cell slidably moves in contact with the underside of the loops so that the volumetric amounts of developer solution in contact with the emulsion is replaced with fresh or less-depleted volumetric amounts of developer solution. Heretofore, however, the distribution of replacement solution throughout the cavity was, to a large extent, unpredictable. It would therefore be desirable to provide a reservoir cell wherein the distribution of replacement solution through the cell cavity is improved.
There are many processing chemicals, e.g., those which possess a pH greater than 11.0, which are susceptible to oxidation or degradation when exposed to air. When such a chemical remains within a cell of the aforedescribed class for a prolonged period of time, such as overnight, the chemical loses some of its effectiveness and may be rendered undesirable. It would be desirable to provide a reservoir cell wherein the likelihood of oxidation of processing solution contained within the cell cavity is substantially reduced so that if the solution is left within the cell for a prolonged period of time, the effects of oxidation of the solution are also reduced.
When devices and systems of the type described are emptied of processing solution, whether by reason of solution change, clean-up or extended periods of non-use, difficulties arise upon refill due to air trapped within the processing cells. Hydraulic characteristics of some solutions include relatively high surface tension properties. While a high surface tension property may be used advantageously for sealing a fully charged cell, the property also disadvantageously supports bubble volumes trapped against a cell roof. These bubble volumes restrict, distort and otherwise inhibit or distort circulatory flow of the processing solution through the cell and prevent a uniform distribution of processing solution reactivity. A means or procedure for purging such a PSM processing cell of solution entrained air would greatly contribute to the process uniformity of the cell. In the case of extremely sensitive, two-sided photo-sensory materials, removal of bubbles from the processing solution, especially developer solution is important.
It is also well known that photographic processing operations are quite sensitive to temperature changes. Depending upon the process, temperatures may need to be held typically within ranges of between .+-.0.5.degree. F. to .+-.2.0.degree. F. from a base temperature for consistency and optimum results. In processing applications of the type with which this invention is concerned, i.e., those involving a relatively small amount of liquid processing solution, and especially, solution disposed in a thin, flowing, liquid film, even a small differential between the temperature of a reservoir cell and that of the working fluid introduced into the cell may alter, e.g., cool, the temperature of the introduced working fluid to such an extent that the temperature of the process operation is outside of an acceptable range. It would therefore be desirable to provide a reservoir cell Wherein the temperature of the working fluid contained therein can be accurately controlled at the point of reactive contact with the PSM object.
An aspect of the present invention is to provide a new and improved system and method of utilizing a reservoir cell of the aforedescribed class wherein the distribution of processing solution throughout the cell cavity is enhanced.
An additional object of the present invention will be to provide a PSM processing cell that presents photo processing solution substantially identically and simultaneously to both emulsion coated surfaces of a two-sided PSM.
A further object of the present invention is to provide a two-sided PSM processing apparatus that circulates processing solution respective to a given process cell over both emulsion coated surfaces.
Another object of the present invention is the provision of a PSM processing cell for simultaneously treating both faces of a two-sided photosensitive film that may be readily purged of atmospheric gas when charged with minimal quantities of processing solution.
Another aspect of the present invention is to provide a new and improved reservoir cell of the aforedescribed class which reduces the likelihood of aerial oxidation of processing solution contained within the cell cavity.
An additional aspect of the present invention is stimulated dispersion of the processing solution within a cell as a result of finely perforated mesh disposed across transverse ridges within the cell cavity.
Still another aspect of the present invention is to provide a new and improved system and method utilizing a reservoir cell of the aforedescribed class wherein the temperature of the working fluid contained within the cell can be accurately controlled.